Why Is My Dog Suddenly Aggressive To Other Dogs?

Dog showing aggression

Over the last year, I have attended 27 dog fights, and I have witnessed an aggressive dog quarreling in a park that led to the death of one of the dogs.

In all these cases, I have noticed a constant pattern between dogs and made me write down notes of the dog’s aggression. This pattern is going to happen each time before a dog fight.

And over 15 fights, the dog owners claimed that their dogs had been the sweetest dogs ever. If that’s the case with your dog, who suddenly wants to bite other dogs, this blog will undoubtedly be for you.

Why Is My Dog Suddenly Aggressive To Other Dogs? A sudden dog aggression may occur due to:

  1. Fear
  2. Adolescence stage
  3. Infections/Physical Pain
  4. Lack Of Socialization
  5. Traumatic Experiences
  6. Early removal of a puppy from his/her mother

You need to understand the exact reason for the dog’s aggression. Using the techniques mentioned here, I guarantee that you will end your dog’s sudden aggression professionally.

How Do Dogs Get Into A Fight?

Dogs growling at each other

I am not talking about the reasons for dogs’ aggression but about why two dogs start to bite each other.

Dogs don’t have complicated emotions. And complicated feelings mean emotions that consist of a group of other emotions. For example, revenge is a complicated emotion as it consists of hate and a willingness to fight back.

On the other hand, dogs only have abstract emotions such as love, fear, stress, hate, etc. These are emotions that consist of 1 feeling and one word.

So why do dogs fight?

To our surprise, dogs fight only for natural canine instincts!

For example, you won’t find dog’s fighting because one dog’s girlfriend started to date another dog in the next neighborhood.

However, they will fight for a variety of reasons which return to their natural instincts:

  • Resource Protection: Maybe a dog wants to protect his food, toys, or water.
  • Protection: Some dogs mark others as a source of the threat, and therefore they react by fighting with them.
  • Over-stimulation: Two dogs were playing with each other and nipping each other in playful behavior. Then suddenly, the small bite changed into a sharp bite, and the dogs started fighting.

All of these reasons are for regular fights. However, there is a mighty reason that causes dog fights, which aggression. This reason is pretty different than the above purposes, as it is a natural instinct in the dog’s behaviors.

What Is Aggression?

Aggression is a sudden feeling of needing to attack anything. For example, dogs might be aggressive towards humans, other dogs, bikers, joggers, cars, etc.

Aggression occurs due to several reasons, but most of them will be concerned with fear or stress.

Aggression is an unnatural behavior in a dog’s pack. It can never be left out, but the dog owner needs to address it quickly and firmly.

Why Are Dog Fights Due To Aggression Dangerous?

Aggressive dogs fighting
Aggressive dogs fighting

So why is aggression scary? After all, a dog fight is just a dog fight, no matter the reason, right?

A typical dog fight is like an agreement between two dogs to fight. Imagine yourself quarreling with someone in the street, you both will reach a point that you know you will hit each other.

However, imagine you were passing by, and suddenly someone lunged from your back and started hitting you aggressively? There will be a difference in your response.

Dog fights due to aggression results in more tragic ends. That’s because one of the two dogs is clueless about the cause of the battle, and didn’t prepare himself to fight back. Therefore, aggression fights are harder than regular fights.

My Own Story About Aggression

I am going to share two stories that I witnessed. One happened with my dog and the other with my friend’s dog:

  1. Mayla is a very stable dog. She never runs to other dogs or tries to tease them at all. One day an Off-leash Perro de Presa Canario started to run to her.

    Unfortunately, a fight between Presa Canario and King Charles Spaniel is unfair, and we will know the results immediately. However, I was lucky that the owner caught him after a few seconds from the fight.

    Now, the dog wounded her in her ears, and we had to go to the vet for some bandages. After that, Mayla developed a fear of Male dogs.

    A few weeks later, Mayla started to develop fear from all dogs and became aggressive towards any dog approaching her.

    A single fight was enough for her to hate all dogs. Luckily, I adjusted her behavior, and now she gets along with other dogs.
  2. I was in a park with my friend’s dog, who is a husky. Bearing in mind that this husky has dominant issues and the owner didn’t neuter him, I was sure there was going to be a problem.

    As a result of multiple males in the park and two females (including my dog), I was very tense with everything around me.

    I advised them to remove the dogs multiple times as there are many male dogs; however, there is no response.

    Things were beautiful until one of the males started to hump a female in the park. Unfortunately, he hit the husky while doing so. As a dominant dog, he began to show his teeth.

    In less than 3 seconds, I have seen four males biting the husky, including a pit bull. Moreover, no one could take back his dog because the dogs were stubborn. Luckily, we ended the fight, and the husky had manageable bruises that quickly healed.

    This husky’s aggression made him enter a fight that could potentially end his life in a min. That’s why you have to speak about your dog’s aggression and don’t ignore it like my friend, the husky owner who knew about this issue and chose to be quiet.

causes Of Aggression

Dog showing aggression
Dog showing aggression

Let’s take a closer look at the triggers of the dog’s aggression towards other dogs:

FearThe number one cause for any behavioral problem will be fear.

Fear makes dogs move unpredictably. Therefore, having powerful & fearful dogs makes an excellent combination of scandals.

Usually, a fearful dog is always put in a “Fight or Flight” situation. He sees other dogs as a threat and thinks that he must deal with this threat fast.

Fight or Flight simply means to fight the threat or run away. Putting a fearful dog in a closed area with some dogs where there is no escape is a real-life-threatening action to all the dogs in the place.

And before you know it, this dog will attack every dog in the place.

Can dogs develop a sudden fear of something?

Unfortunately, yes, and it may happen very fast before you can take notice. A lot of times, I see my dog suddenly afraid of something that she used to do.
A dog who is fearful of other dogs might need help over the long run.

Meaning that there isn’t an overnight fix, but instead, you have to be consistent and go through it with your dog.

Dog’s fear of other dogs is usually due to a lack of trust. Therefore, if you could get back the dog’s confidence in other dogs once more, you will resolve the issue.

If you have a friend who has another calm and stable dog, then you are lucky. Introducing this dog calmly to your dog will be very helpful.

Whenever you introduce a new dog to your dog, try not to push him. Make sure to leave enough space for him to run away and stay behind. And always give him treat and praise when approaches the new dog.

If you follow those tips for every new dog that meets your dog, you will find your dog slowly gaining back confidence, and get over the fear.

It needs patience.
Age IssuesTwo stages in the dog’s life have a significant effect on his behavior, adolescence, and the seniority stage.

A dog who has just hit adolescence requires lots of patience. The adolescent stage starts around ten months and lasts until 1.5 years.

During this period, your dog might pass through several changes that lead him to be suddenly aggressive.

Unfortunately, many owners release their dogs away at this age because they can’t deal with them.

The seniority stage won’t have any issues unless your dog is suffering from some health issues. If he does, then you have to take extra care.
First and foremost, understand that you have to build a bond with your dog.

You have to convince the dog to love you, follow your guidance, and not force him to do so.

You also have to realize that you have to deal with any dominant issue firmly.

Don’t let the dog do whatever he wants and, at the same time, try to prohibit him smartly without using aggressive techniques like yelling.

Remember that allowing the dog to do unwanted behavior once will result in a nasty attitude over the long run.

I recommend this article, which talks about this stage in depth.
Physical IssuesWhen your dog is in pain, he might turn aggressive suddenly, especially when touching the aching part of his body.

Typical physical pain is hip dysplasia. Many dogs develop this disease over time, and without the owner’s noticing, this can be very painful for your dog.

So your dog might be playing with another dog, and suddenly the strange dog napped his aching area. And you will have an aggressive dog because of that.
Schedule an appointment with the vet to have a quick checkup on your dog, especially if it shows other pain symptoms like limping.
Infections in GeneralAny infection that makes the dog uncomfortable might turn him aggressive.

My dog turns aggressive when she catches the flu, which becomes a robust sign for me that she is ill.
If your dog shows symptoms like laziness, vomiting, or diarrhea, then schedule an appointment with the vet.
Traumatic ExperiencesRemember my dog’s story that I just shared in the beginning?

When a strange dog bites your dog, your dog will most likely develop a behavioral issue against strange dogs.

But not only biting that can make your dog aggressive to other dogs.

If your dog was beaten at his young age, he might also be at the edge of the cliff and ready to be aggressive at any time.

That’s the problem with many rescue dogs. What new owners don’t know that rescue dogs most probably have hidden issues that they need to address carefully.

And no, the dog might not show any symptoms of aggression and just break out suddenly in a moment.
These cases are extraordinary, and seeking an expert is a must.

My recommendation is to prevent your dog from meeting any strange dogs until you have an expert who can improve your dog’s behavior.

If you can’t see an expert, follow some tips, but please take extra care.

What you are dealing with here is frightening, especially if you don’t know your dog’s past experiences.

The first thing we need to do is to figure out how bad the situation is. You can do this by introducing a strange dog to your dog behind a fence.

Take care that a single mistake is enough to get you in trouble.

By doing so, you can get an idea of how bad the situation is. If your dog shows symptoms of high aggression like trying to bite and not only barking/growling, this means that you need to work hard.

First, try to introduce him to as many dogs as possible behind a fence and keep a long distance between them.

Shorten the distance every time and make sure that your dog is relaxed with this distance.

DO NOT introduce dogs without a fence until you have an expert around. Dogs might seem pretty cool, but once they meet face-to-face, they will fight.
Stacked EventsDid you watch the Joker movie?

In this movie, we can see the Joker, who was previously a clown, suddenly turning into a killer. However, he had stacked events that made him a killer.

Applying the same concepts to your dog, you might find that there are small events that happen to your dog that might turn him into an aggressive dog.

For example, hitting a dog multiple times might not have an immediate effect. However, in the long run, you can clearly see an unstable dog.

Your dog might have witnessed experiences from other dogs like taking his toys, etc.

Those experiences stacked until he turned into the suddenly aggressive dog over the night.
To fix something like that, you need to apply the same procedures used in treating fear.

Not only to follow the procedures, but you have to take a closer look at how the dogs deal with each other.

Avoid anything interaction with your dog’s belongings even if you see it pretty average.

For example, prevent the other dog from taking your dog’s toys or drinking from his water.
Lack Of SocializationA lot of people miss an essential key in their puppy’s life, which is socialization.

You can’t imagine how socialization can change your puppy’s life.

Socialization makes your puppy comfortable with other dogs, cats, joggers, bikers, etc.

Missing socialization is a problem that I see a lot, especially with guarding dogs, because some people have a misconception about them.

Some people think that letting your puppy play with other people/dogs make him over friendly.

In fact, socialization builds your dog’s brain to understand the type of friendly people and the other kind who is evil.

The same concept applies to strange dogs.
Socializing an old dog is a bit hard.

A good trick that I use with old dogs is to go out with a bag of treats and let strangers feed him and pet him.

I also pass by dog parks and make sure that he sees other dogs who are playing and enjoying.

I take older dogs frequently outside to different places and make sure they see different people/dogs.

If your dog sees the same neighbor’s dog daily, this can’t be considered as socializing.

Socializing means getting your dog to see strange dogs and people and getting along with them.
Early removal from motherI am firmly against the early departure of the dog’s mother.

A lot of breeders send puppies home around the age of 8 weeks, which is really early.

Mother has a significant role in teaching her puppies some behaviors like cleaning themselves.

Another vital role of the family is biting inhibition.

When puppies get a chance to play with each other, they learn an essential aspect: how to play without hurting each other.

Usually, when a puppy hurts his brother, he will scream, indicating that he doesn’t want to play anymore.

This way, your puppy learns how to play correctly.

Another important aspect is that puppies understand the difference between playful behavior and attacking.

A lot of fights and aggression happen due to the miscommunication between dogs.

If a dog can’t differentiate between playful behavior and attacking, he will most likely be aggressive to any playful behavior.
If your dog is still a puppy, then what you can do is to let him play with other puppies as much as possible.

However, I am sure you have a large old dog now. And unfortunately, you can’t do anything about it except by fixing the behavioral issues on their own.

If that’s the case, by following the same steps mentioned in the fear section and the general tips, you can help your dog.

Diagnosing Aggression Reasons

Dog receives training
Dog receives training

So, how can I determine my dog’s main issue?

Determining your dog’s main issue needs some intelligence, observation, and try-and-error. However, as I always say, a dog’s aggression issues should be handled by professionals.

So, if you are not confident about the next steps, then please don’t do them.

To determine your dog’s issue, do the following:

  1. Look at your dog’s life. Try to remember any events that happened to your dog, and then suddenly, he became aggressive. If you couldn’t find any, then your dog isn’t aggressive because of Stacked Events or Traumatic experiences.
  2. If you had a rescue dog from a shelter, try to call them and ask about the dog’s past life. Did his previous owner abandon him? Was he found beaten?

    If you can’t know anything about his previous life, then I am sure than 50% of his past life was horrible, and that might be the trigger for aggression.
  3. Now try to identify the exact time that your dog turned into an aggressive dog. If you found that this time was around 10-11 months, your dog passed through a teenage stage.
  4. If every point from the above doesn’t apply to your dog, schedule an appointment with the vet to check your dog’s health.
  5. If your dog appeared perfectly in good health, then the issue is mental.
  6. Get a dog’s muzzle and let your dog wear it. Don’t say that you will hold your dog. Dogs can get really tough.
  7. Set the place in your backyard to have a barrier that your dog can’t exceed or buy a kennel for your dog.
  8. Bring a steady, stable, and friendly dog.
  9. Now it’s time for some try and error.

    Observe your dog’s body when the strange dogs enter the backyard, is he tense? Or relaxed?

    A tense dog will have a standing hair, sharp eyes, full-body leaning forward, and some pointing ears.
  10. If your dog is tensed from the first moment the dog enters the backyard, your dog’s main problem is fear. He is afraid of dogs.
  11. If he only growls when the strange dog is too near, he has some insecurities, and maybe he didn’t learn puppy inhibition.
  12. Generally, having him exposed to as many dogs as possible in a safe way is going to help. As mentioned, start by having a dog standing at a very far distance and gradually decreasing the distance while making sure that your dog is relaxed.
  13. Level up the game gradually by introducing the dog without kennel while on the muzzle and praising him.
  14. Then if your dog is relaxed, remove the muzzle carefully while holding the leash.
  15. If your dog isn’t OK with that, go a step backward and practice more until your dog is comfortable.
  16. Always keep in your mind that you must follow safety guidelines mentioned here, and don’t ignore them because your dog is relaxed.
  17. Start walking him around other dogs and dog parks to make him comfortable around them.
  18. Step up the game by entering a dog park while keeping him on a leash in the entrance.
  19. Gradually increase his interaction while praising and make sure that you don’t expose him suddenly to a situation that is stressful to him.
  20. If nothing is working, please stop and call assistance.

Training And Behavioral Adjusting.

Dog getting behavior adjustment training

As you are dealing with this aggression, you need to train your dog. First, you need to master obedience training, and then you can choose whatever tricks you want.

A lot of people don’t understand the link between aggression handling and obedience training.

Obedience training, in general, is beneficial in a lot of situations. As it increases the dog’s bond to you, it helps as well protect your dog from a lot of harmful conditions.

Another essential aspect to consider is behavioral adjusting.

Here a useful technique that you can use is scenario-based training, as this creates the perfect opportunity for safe learning.

For example, you can bring a friendly dog home to create some distraction for your dog and then train him to leave this dog and come to you instead. After that, you can move this training to the street and level it up a bit.

When Mayla was eating from the street, I decided to use scenario-based training. I put some food on the ground at home and prohibited her from touching them, and then I gave her treats.

The beauty of scenario-based training is that you can adjust the scenario to your need. You can increase or decrease the difficulty, and you have a safe environment to practice. For example, if my dog ate what I have put for her while training her, it won’t harm her, unlike street food.

That’s why I always use this training when dealing with aggressive dogs to make sure that I rehab him to deal with other dogs correctly, and it works like a charm!

Get It Off Your Chest

I hate to see that some owners are shy to say that they have an aggressive dog.

I know it sounds heartbreaking that your sweet poodle is aggressive, but you have to be responsible and protect him.

My friend in the above story knew that her husky is aggressive, and she chose to keep it as a secret, and as a result, we were about to lose him.

Be brave and honest, and understand that there is no shame to have a dog with a behavioral problem. People will appreciate your honesty.

Will The Treatment Be Permanent?

A dog with a severe behavioral problem will not get back to the normal state immediately. It takes years and years of practicing and reinforcing new concepts.

The treatment will be permanent if you stick to the guidelines. However, many people just stop training or adjusting behavior once they see their dog playing happily with other dogs once or twice.

Make sure you revise your dog carefully and that he is comfortable around other dogs. Time after time, your dog will get better until the changes become permanent.

I believe it took my dog nine months to overcome her fear of dogs, which is an extended period. However, I had to make sure that my dog is relaxed and that I don’t push her to do something stressful.

How To Stop A Dog Fight

Now I would like to share some tips that I strongly recommend every owner to know. Whether your dog is aggressive or not, you have to understand how to stop a dog fight.

Dog fights seem pretty stressful, and they require a few techniques that ensure your safety.

I see people just get it and try to grab the dogs’ mouths, and they get bitten. Or try to pull the dogs away from each other firmly while they are holding each other.

First of all, a dog’s mouth is very tough. Once your dog decides to look firmly on something, it’s hard to open his mouth (almost impossible.)

Moreover, if the fighting dogs are muscular breeds like Pit bull, Rottweiler, Persa Canario, Doggie Argentino, etc., you will have no chance of opening their mouths at all.

A fight between muscular dogs need quick movements; those mouths can easily damage each other. Some tips that you need to stick to:

  1. Try to distract the fight:

    Distracting the dogs who are fighting is a proven working way, and you can do it by different methods:
    1. Throw water over the dogs’ faces. This forces them to close their eyes and step back. Try to throw the water fast that it annoys them, not just pour water on their heads.
    2. If you have anything that produces a loud noise, use it. Air horns or any high-intensity sound can break them from each other.
    3. Throw a blanket or cover over the dogs. This way, you will block their eyesight. You can use a piece of clothes or anything that will prevent their sights.
  2. If the dogs were very fierce and distracting didn’t help, use the wheelbarrow method. If you have a friend or any person standing aside, make him lift the dog from his back legs/hinds, and you do the same with your dog.

    By doing so, you will be sure that both dogs don’t have the strength to fight and will leave each other.

    DO NOT use the wheelbarrow method if you are alone. Doing so makes it easier for the other dog fighting back to have a better grip on yours and just worsening the situation more.
  3. The last thing is to use objects around you to separate them from each other. You can use a chair or a stick or anything to separate them. Never hit any of them, just try to separate them safely.
  4. Once the fight stops, you must separate the two dogs.

    You have to understand that a dog who just fought is really stressed and can’t think of what he is doing. So keep calm and try to handle the situation like a pro.

    Shouting or yelling doesn’t help. You need to be fast and to think quickly. Try to get hold of each dog slowly.

    If you are alone and there is a strange dog, stay in the middle between the two dogs to push both dogs apart until you can safely withdraw yourself and your dog.

Now we need to cover some mistakes that worsen the dog fights:

  1. If you’re in a park, and some strange dogs started to fight, please get hold of your dog and step back.

    Dogs get stimulated quickly, and a fight between two dogs can trigger many more dogs to enter and bite. So by holding the nonparticipating dogs, you are helping by preventing the fight from scaling.
  2. Do not hit dogs, do not hit dogs, do not hit dogs.

    Hitting a dog won’t make him step back, but he will start biting harder after each time. Each hit makes the dog more aggressive and angrier until he wants to kill the other dog.
  3. Don’t try to grab a dog from his neck by a leash because it makes him angrier.
  4. Do not use treats or food as a distraction, it won’t work, and you will waste time.
  5. DO NOT make the dogs play with each other again after a fight, they need to take a break for some hours.
  6. Do not use another dog to break a fight, except if that dog was trained to do so. My friend has a service dog who is trained to handle situations like that. He can go into a fight, set the dogs apart, and bark at each dog individually.

Make sure to send your dog to a vet after the fight.

How To Prevent A Dog Fight In The First Place?

Prevent dog fights in the first place

I hate to see that some owners are shy to say that they have an aggressive dog.

  • If you are in a park, then make sure there isn’t a female dog in heat with some unspayed males. If that’s the case, I am 1999% sure that there will be a fight.

    That’s because wolves fight each other to determine who is the strongest to marry the female. And the same concept applies to dogs.
  • Generally, try to be in a park that has a maximum of 4-5 dogs at once. If the park has more than five dogs, you will have a high chance of breaking out a fight.
  • If you were walking your dog and noticed a dog who is running at you full speed, then you have to be prepared. Don’t run. If you turned into a defensive state, then you are most likely going to be bitten.

    Instead, try to lunge forward in the direction of the dog. Usually, all the dogs, when I do that, get confused and step back. That’s because you show them how confident you are.

    Try to show him a steady body posture ready to fight, and the attacking dog will return running.
  • If you noticed two dogs crawling or barking, then quickly place yourself between them and start pushing them apart.

    Most likely, dogs show some signs before fighting if you are a reasonable observer, you can prevent a lot of fights.

Playful Behavior VS A Real Fight

Puppies playing
Puppies playing

A lot of people miss the difference between nipping and real fights.

When you see my dog while she is playing with her best friend Golden Retriever, you would think that they will kill each other.

However, they never hurt each other. That’s the importance of biting inhibition. They know how to bite and wrestle with each other, but you can never see any wound because they don’t harm each other.

Therefore, you have to differentiate between playing and fighting. Usually, dog’s play contains wrestling and biting, and consequently, you don’t need to stop that.

However, a real fight contains whining, crying, and actual biting.

How To Help Dogs Get Along After The Fight

Dogs can definitely get along after fight and after behavioral adjustments. However, they will never be able to play as the best pals.

That’s because they will forever remember what happened, and they would try to ignore each other as much as possible.

There is nothing you can do except training them, making them meet each other behind a barrier and start to train them together.

Try to involve them in fun games with you, but never let them alone again until they start to overcome what happened.

If the fighting dogs live under the same roof, you have to call a professional to help you with this issue.

How To Treat Wounds

After a dog fight, there must be some wounds.

While you can first aid them, you have to go to the vet if the wounds were in dangerous places like beside the eye for checkups. Also, if the scars caused any swelling around them, then you have to see the vet.

However, for simple wounds, I recommend Cesar Millan’s amazing article that covers this in-depth. There are many variations, and you need to determine the type of injury.


Dog’s sudden aggression may occur for a lot of reasons. As an owner, you need to have patience and be ready to handle such aggression.

Ensure that you know the basics of first aids or how to handle dog fights, as they can really help you a lot whenever a fight breakout.

Always remember that the key to success is to be consistent, don’t stop training your dog once his aggression stops.

Erwin Borgers

Hi, I’m Erwin. I grew up with two cats, but I always wanted to have a dog. Since my wife and I lived together, we have Mayla. She is a very sweet King Charles Spaniel. Together we spend countless of hours in the forest near our home. We love to walk together and now I want to share what I learned about walking dogs and what I learned about dog gear with you.

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